Answer: A) A colon after "countries."
Explanation: a colon is a punctuation mark used to mark a major division in a sentence, to indicate that what follows is an elaboration, summation, implication, or explanation of what precedes. In the given sentence we should put a colon after the word "countries" because then we are listing the countries which is an elaboration of the previous part of the sentence. The complete sentence would be: I've visite three other countries: Ireland, England, and France.